The present invention relates to a plate cylinder for a web-fed printing press having a device for securing flexible printing plates provided with bent ends mountable on the circumference, an installation channel accessible through an entrance slot on the circumference being provided, the channel being limited on one side of its input area by a wedge-shaped lip edge on one side for engaging the front ends of the plates and at least one profile body being secured therein, having at least one holding device that can be engaged with the rear end of at least one printing plate.
An arrangement of this type is known from German Patent Document DE 102 55 707 A1. The holding device assigned to the rear ends of the plates is formed there only as a clamping mechanism which is unable to execute any chucking movement. However, this has proven to be a disadvantage in many cases.
Against this background, the object of the present invention is therefore to improve upon a device of the generic type with simple and inexpensive means so that a reliable chucking force can be applied to the rear ends of the plates.
This object is achieved according to this invention by the fact that the holding device assigned to the rear ends of the plates includes a tension strip that is accommodated on the profile body and is moveable toward the entrance slot and away from it and an actuating device installed in the profile body and assigned to the former, the actuating consisting of a lifting mechanism and a return mechanism that counteracts this, whereby the tension strip can be engaged by means of the lifting mechanism in an assembly position approaching the entrance slot, in which position the rear end of each assigned printing plate can be engaged on a suspension claw on the tension strip and can be brought into tension engagement with the rear end of each respective printing plate by means of the return mechanism.
These measures yield a mounting device having a high level of safety and reliability. At the same time, these measures ensure such a compact arrangement that despite the use of a displaceable tensioning bar, the complete mounting device assigned to the rear ends of the plates is situated on the profile body. The inventive arrangement therefore makes due with only one cylinder recess assigned to the profile body per mounting device in an advantageous manner, the cylinder recess practically forming a joint design space for the tensioning bar and the lifting and restoring mechanisms assigned thereto. Multiple design spaces and thus multiple cylinder recesses are not necessary in a advantageous manner. Therefore an inadmissible weakening of the cylinder can be avoided easily. Another advantage of the measures according to the present invention may be regarded as the fact that despite permitting a reliable plate tension, a comparatively narrow input cross section of the cylinder recess is possible, i.e., a comparatively narrow interruption in the circumference of the cylinder. This ensures that as a rule no bearer rings are needed, and furthermore, excitation of the inking rollers to vibration is largely suppressed.
At least one clamping spring adjacent to the tensioning bar may advantageously be provided on a profile body, the clamping spring coming to rest against the inside flank of the lip edge assigned to the front ends of the plates. This clamping of the front ends of the plates increases reliability. The clamping springs provided for this purpose also advantageously eliminate the need for clamping with the help of a tensioning bar, which would in principle also be possible, so that the lift of the latter may also be comparatively small, which has an advantageous effect on the compact design that can be achieved. The great advantage deriving from a compact design can be further increased by the fact that the profile body has a cutout facing the tensioning bar and optionally the clamping spring in the circumferential area facing the entrance slot.
In another refinement of the primary measures, the profile body may have a channel assigned to the actuating mechanism of the tensioning bar, boreholes emanating from this channel so that tappets carrying the tensioning bar and cooperating with the actuating mechanism engage in these boreholes. The tappets may be guided in the boreholes, which permits a high degree of reliability. At the same time, these measures also allow the design space assigned to the actuating mechanism to be sealed with respect to the area of the installation channel that is open via the entrance slot, which in-turn results in reliable protection from damage and soiling.
A particularly comfortable embodiment of the lifting mechanism may consist of the latter having a lifting cushion that engages beneath the tappet and can be acted upon by a pressure means. Such an arrangement also operates with especially low wear.
Another advantageous embodiment of the lifting mechanism may consist of the fact that it has a pusher rod displaceably arranged in the respective channel of the profile body, so that startup elements provided for lifting the tappets and ramp elements cooperating with the former can be moved by means of these pusher rods in relation to one another. This mechanical solution to the problem has proven to be particularly stable.
The pusher rod may expediently contain the startup elements preferably designed as startup rollers and may be accommodated on casters. This yields an especially compact arrangement which is at the same time very smooth running.
In this context, another advantageous measure may consist of the fact that the profile body is designed in two parts and has an attachment having a roller surface assigned to the pusher rod, closing the channel which accommodates the pusher rod. This attachment may advantageously be made of a high grade material and/or may be hardened to obtain a high quality running surface.
Other advantageous embodiments and expedient refinements of the primary measures can be derived in greater detail from the following description of a few exemplary embodiments with reference to the drawings.